Generally, in the manufacturing process for an integrated circuit, most of semiconductor devices are formed through a serial processes, such as deposition, photolithography, or etching process, in order to smoothly accomplish the device fabrication.
In the manufacturing process of integrated circuit, oxides (e.g. silicon dioxide) or nitrides (such as silicon nitride) are often used as mask materials. For. example, silicon nitride mainly includes two functions: (1) during the manufacturing process of metal oxide semiconductor (MOS) device, it is necessary to form a silicon nitride layer by low pressure chemical vapor deposition (LPCVD) to serve as an anti-oxidative mask when conducting the growth of an oxide layer; in addition, a silicon dioxide layer is further formed between the silicon substrate and the silicon nitride layer to serve as a pad oxide to prevent the silicon nitride layer from being directly formed on the silicon surface which may results in an overhigh stress; and (2) during the trench etching process, the silicon nitride layer is used as an anticorrosive passivation layer, generally utilizing the combination of the silicon nitride layer and the silicon dioxide layer, and formed by plasma-enhanced chemical vapor deposition (PECVD); because it functions as a passivation layer, the anticorrosive property is very important; on the contrary, in order to perform a peeling process (i.e. the finally etching process), the used material must be selectively etched, that is, using a suitable etching solution to perform the peeling process.
From the above description, it is found that the combination of the silicon nitride layer and the silicon dioxide layer can be applied to many aspects. However, for the commonly used mask materials such as silicon nitride and silicon dioxide, their formed way, i.e. CVD, not only spends a lot of equipment costs but also causes some additional problems due to high-temperature growth. In addition, if the silicon nitride layer is directly formed on the silicon substrate, it will result in a high stress on the silicon surface. Because the adhensive ability of the silicon nitride layer to the silicon substrate is relatively poor, a silicon dioxide layer must be formed between the silicon nitride layer and the silicon substrate during the deposition process so as to successfully form a silicon nitride layer on the silicon surface. However, this step also increases the complication of the manufacturing process. If a single-layer material can be substituted for the combination of the silicon nitride layer and the silicon dioxide layer, it will greatly enhance the efficiency of the growth process.
More importantly, in the current chemically etching process for removing the silicon nitride layer, hot phosphoric acid is used to peel off it. Its etch rate is about 60 xc3x85/min. However, there still exists the necessity of improvement to meet the requirement of the current industry of integrated circuit.
An object of the present invention is to provide a method for forming a titanium dioxide layer on a device.
Another object of the present invention is to provide a titanium dioxide layer serving as a mask used in a manufacturing process of an integrated circuit and its removed method.
The method includes the steps of forming a titanium dioxide layer on the integrated circuit device to serve as the mask, and using an etchant to selectively remove the titanium dioxide layer.
Perferably, the integrated circuit device is a silicon wafer.
The titanium dioxide layer is formed by the steps of providing a titanium-containing material, adding an acid substance to the titanium-containing material to form a mixture, and exposing the integrated circuit device to the mixture to form the titanium dioxide layer thereon. The titanium-containing material is preferably H2TiF6 and has a concentration ranging from 2.0M to 6.1M.
Preferably, the acid substance is one selected from a group consisting of nitric acid, boric acid, hydrogen chloride, and a mixture thereof. The concentration of nitric acid preferably ranges from 0.1M to 0.5M. The concentration of boric acid preferably ranges from 0.1M to 0.9M. The concentration of hydrogen chloride can range from 0.001M to 2M.
In accordance with the present invention, the titanium dioxide layer is formed by a liquid phase deposition at a temperature ranging from 20xc2x0 C. to 80xc2x0 C. Besides, the cleaned integrated circuit device is exposed to the mixture for 2 to 30 minutes.
The etchant can be phosphoric acid. The temperature change of phosphoric acid is used to control the etch rate of the titanium dioxide layer. The temperature of phosphoric acid can be greater than 100xc2x0 C., preferably from 100xc2x0 C. to 180xc2x0 C., and the concentration of phosphoric acid ranges from 1% to 85%.
The present invention may best be understood through the following description with reference to the accompanying drawings, in which: